This invention relates to surgical needles, and in particular, needles used for endodontic procedures, such as root canal surgery. During endodontic procedures, such as root canals, it is necessary to inject or applicate fluid into the dental pulp or root. Presently, typical needles used for these types of procedures are made from relatively inflexible stainless steel. This material has been preferred for its ability to be autoclaved and its relatively inexpensive cost; however, use over time in endodontic applications has revealed several undesirable characteristics. For example, a typical tooth has at least one root. Each root is not straight, but curves toward the centerline of the tooth. The relative rigidity of stainless steel has led to unwanted results when used in root canal surgery due to the needle""s inability to bend to the contour of the curved root canal. During a root canal procedure, a dental practitioner drills an opening in a patient""s tooth surface enamel and inner dentine to gain access to the dental pulp and surrounding cavity. A hollow, stainless steel surgical needle is inserted into the opening to remove decaying pulp tissue and irrigate the surrounding cavity with sodium hypochlorite solution. The sodium hypochlorite solution rids the canal of bacteria and other foreign substances before sealant is injected into the canal. The dental pulp cavity is curvately elongate and tapers into the root area of the affected tooth. The rigid nature of a stainless steel needle does not allow the flexion necessary to move through the delicately curved root cavity to reach the most distal end. At present, the dental practitioner must exert extreme care in using the stainless steel needle to avoid puncture of the tooth wall and surrounding jaw. Common dental practice at this time is to pre-bend the needle prior to insertion using an X-ray image as a template. Although pre-bending allows the dental practitioner to insert the needle into the root canal somewhat farther than when the needle is left straight, this method is crude at best and full access to the root canal apex cannot be achieved. Should the dental practitioner meet needle resistance during insertion, he must discontinue insertion or risk damage of the tooth and surrounding area. If this occurs, the practitioner must be satisfied with partial depth insertion and subsequent partial irrigation. The tip of the root cannot be accessed so completely so full aspiration and irrigation cannot be accomplished. If the dental practitioner continues insertion after meeting curvature resistance, the risk of punching a hole in the tooth wall becomes great.
The practice of using endodontic surgical needles fabricated from nickel titanium (NiTi) stainless steel is known under the teachings of U.S. Pat. No. 5,000,912 issued to Bendel et al among others, in addition to other nickel titanium alloys disclosed in U.S. Pat. Nos. 4,337,000; 4,565,589; 4,505,767; 4,770,725 and European Patent EP 0 529 675 B1, also granted to Bendel et al. The use of this alloy in connection with conventional endodontic needles has not achieved desired results. The present invention contemplates fabrication of endodontic surgical needles of an alloy of nickel and titanium, per se, including a stainless steel sleeve to allow for manual fixed-angle adjustments in the upper portion of the needle, and a modification of the distal end of the needle to provide a skived, side-vented area.
It is therefore an object of this invention to provide an autoclavable endodontic needle assembly capable of curving to the configuration of a root canal while being inserted therein. The needle is preferably fabricated from a binary NiTi alloy. The preferred binary NiTi alloy contains 55.8 weight percent Nickel. The needle of the present invention may be produced to be pre-bent to a desired angle; the preferred angle chosen is 45 degrees. The present invention may also include an angle-adjustment sleeve around a portion of the needle to allow for manual adjustment of the pre-bent angle. An adhesive-filled supporting hub member grippingly engages the needle shaft to provide connection to a conventional luer lock. The supporting hub configuration may also be pre-bent to a desired angle, such as 45 degrees, with the protruding needle shaft being straight. The options of straight or pre-angled needle, straight or pre-angled hub portion, and manually adjustable angling sleeve are conceived to give the dental practitioner convenient options for ease of use while working within the awkward confines of a patient""s mouth.
Sodium hypochlorite solution, depending upon the solution strength, can be a caustic solution and may have an adverse affect on the preferred binary NiTi alloy. To substantially eliminate the possibility of the solution corroding or deteriorating the NiTi alloy, a coating, such as a parylene polymer, is applied to the needle during its manufacture. While parylene polymers are the preferred coatings, there are other commercially available coatings that provide the same protection. The coating prevents the sodium hypochlorite solution from adversely affecting the physical properties of the dental needle.
It is a further object of the present invention to provide a unique tip for the needle. The tip portion of the present invention includes a skived area at the most distal end of the needle. The skived area allows side venting of irrigation fluid and prevents vacuum build up during aspiration of the root canal. The unique tip is further capable of functioning within the narrow and curved confines of a root canal.